Effective Java 第二版 Enum

/** * Effective Java 第二版 *   第30条：用enum代替int常量  */

import java.util.HashMap;import java.util.Map;

public class EnumTest {

    /*媒体操作*/    public final static int START = 1;    public final static int PAUSE = 2;    public final static int RESUME = 3;    public final static int STOP = 4;

    /*返回结果*/    public final static int RET_OK = 1;

    private static int playWithInt(int fun)    {        switch (fun)        {            case START:            case PAUSE:            case RESUME:            case STOP:                System.out.println("playWithInt do " + fun);                break;            default:        }        return RET_OK;    }

    public enum PlayEm    {        START,PAUSE,RESUME,STOP //命名空间使得他可以重名    }

    private static void playWithEnum(PlayEm fun)    {        switch (fun)        {            case START:            case PAUSE:            case RESUME:            case STOP:                System.out.println("playWithEnum do " + fun);                break;            default:

        }    }

    public enum SuperPlayEm    {        START(1,"START"),PAUSE(2,"PAUSE"),RESUME(3,"RESUME"),STOP(4,"STOP");

        private final int code;        private final String name;

        SuperPlayEm(int code, String name) {            this.code = code;            this.name = name;        }

        @Override        public String toString() {            return "SuperPlayEm{" +                    "code=" + code +                    ", name=‘" + name + ‘\‘‘ +                    ‘}‘;        }

        public void doPlay(String player)        {            switch (this)            {                case START:                case PAUSE:                case RESUME:                case STOP:                    System.out.println("player : "+ player + " exec " + this.name());                    break;                default:            }

        }    }

    private static void playWithSuperEnum(SuperPlayEm fun)    {        switch (fun)        {            case START:            case PAUSE:            case RESUME:            case STOP:            default:                System.out.println("playWithSuperEnum do " + fun);        }    }

    public enum SuperPlayApplyEm    {        START(1,"START"){void doPlay(String player){System.out.println("player : "+ player + " exec START" );}},        PAUSE(2,"PAUSE"){void doPlay(String player){System.out.println("player : "+ player + " exec PAUSE" );}},        RESUME(3,"RESUME"){void doPlay(String player){System.out.println("player : "+ player + " exec RESUME" );}},        STOP(4,"STOP"){void doPlay(String player){System.out.println("player : "+ player + " exec STOP" );}};

        private final int code;        private final String name;

        SuperPlayApplyEm(int code, String name) {            this.code = code;            this.name = name;        }

        @Override        public String toString() {            return "SuperPlayEm{" +                    "code=" + code +                    ", name=‘" + name + ‘\‘‘ +                    ‘}‘;        }

        abstract void doPlay(String player);    }

    public enum MixEnum    {        START("400100","1001"),        PAUSE("400100","1002"),        RESUME("400100","1003"),        STOP("400100","1004")        ;        private final String baseCode;        private final String followCode;

        private static final Map<String,MixEnum> map = new HashMap<String,MixEnum>();

        static {            for (MixEnum mixEnum : MixEnum.values()) {                map.put(mixEnum.baseCode+mixEnum.followCode,mixEnum);            }        }

        MixEnum(String baseCode, String followCode) {            this.baseCode = baseCode;            this.followCode = followCode;

        }

        public static MixEnum fromCode(String code)        {            return map.get(code);        }    }

    public static void main(String[] args) {　　　　/*P128-P134*/

        //传统C做法        playWithInt(START);  //打印无法识别        playWithInt(RET_OK); //编译器不能报错

        //普通java枚举        playWithEnum(PlayEm.START);//        playWithEnum(RET_OK);

        /**         * 自定义java枚举         */        SuperPlayEm aaa = SuperPlayEm.START;        playWithSuperEnum(aaa);

        /**         * 打印所有枚举信息         * 如果有人要一份接口文档时，是不是会很好用         */        for (SuperPlayEm superPlayEm : SuperPlayEm.values()) {            System.out.println(superPlayEm);        }

        /**         * 这个枚举可以做的很强大，给他设置很多参数，也可以定义函数         * 但这样做可能在加一个枚举的时候，忘记加case分支         */        aaa.doPlay("camera");        /**         * 防止忘记加case         * 但这样导致代码变多，各有利弊吧。         */        SuperPlayApplyEm superPlayApplyEm = SuperPlayApplyEm.PAUSE;        superPlayApplyEm.doPlay("camera");

        /**         * 生成枚举的方法 1  valueOf         */        SuperPlayEm superPlayEm = SuperPlayEm.valueOf("START");        System.out.println(superPlayEm);

        /**         * 生成枚举的方法 2   自定义         *         */        MixEnum mixEnum = MixEnum.fromCode("4001001002");        System.out.println(mixEnum);    }

}

原文地址：https://www.cnblogs.com/aoyihuashao/p/9053959.html